Using dehistonized chromatin preparations, we have elicited antisera which react immunologically with chicken erythroid and HeLa cell chromatins. The antisera are highly specific and localize in the cell nucleus. According to our studies, the antigen is a complex of chromosomal proteins with DNA. Both the protein(s) and the interacting DNA segments will be isolated and characterized in search of their biological significance. Using specific globin cDNA probes, we will continue our studies on the in vitro transcription of globin genes in isolated chicken erythroid chromatin. The effects of chromosomal nonhistone proteins and chromatin structure on the transcriptional regulation of specific genes will be investigated.